Arthroscopic surgery involves using optical instruments, such as an arthroscope, to visualize an operating field inside or near a joint of a patient. The same instrument or other instruments may be used to perform a surgical procedure in the operating field. Common instruments used in addition to the arthroscope include a trimming instrument for cutting tissue and an irrigation instrument for irrigating the surgical field. Each of the instruments requires its own incision to be introduced into the surgical field. Thus, many surgeons prefer to use only a trimming instrument and an arthroscope during arthroscopic surgical procedures.
Arthroscopes are fragile in relation to the forces applied during arthroscopic surgery, so a rigid cannula is placed over the arthroscope to reinforce it. The distal end of the rigid cannula is pointed, usually sharp, and thus the rigid cannula can scratch or gouge soft tissue within the operating field. The rigid cannula can also become stuck between bones or cartilage during a procedure. The metal surface of the rigid cannula can also damage metal prosthetics used to replace joints, resulting in a shortening of the useful life of the prosthetic and forcing the patient to undergo additional, painful surgeries to correct the problem.
An additional problem associated with arthroscopic surgery is maintaining a clear surgical field during surgery. Blood and debris can cloud the field, impairing a surgeon's ability to visualize tissue. One method of solving this problem is to use the irrigation instrument to clear the surgical field with saline. However, many surgeons strongly prefer to avoid the additional trauma caused by inserting a third instrument.
Known inflow and outflow endoscope systems introduce an irrigating fluid into the surgical site, thus obviating the need for a third instrument. For this purpose, the endoscope has an inflow channel defined by the inner surface of the sheath. The fluid passes through the channel and exits the distal end of the sheath to irrigate the operative site. Fluid at the surgical site may be withdrawn through an outflow channel defined by the outer surface of the inner sheath and the inner surface of a surrounding outer sheath. The outflow channel originates at the distal end of the instrument and transports fluid to an exit point at the proximal end of the outer sheath. The larger diameter of these systems requires larger and more traumatic surgical portals.
In arthroscopic surgery, as well as other surgical procedures, there remains a significant need for improved techniques that reduce the size of the portals while providing substantially continuous and properly managed fluid inflow and outflow. The Applicant's co-pending application Kucklick, Atraumatic Arthroscopic Instrument Sheath, U.S. application Ser. No. 11/094,626 filed (Mar. 29, 2005) describes an inflow/outflow sheath that reduces the diameter of the continuous flow system while properly managing surgical site fluid inflow and outflow. The inflow/outflow sheath is a tube having inwardly extending ribs that form multiple lumens when an arthroscope is inserted. The proximal portion of the sheath is provided with fluid ports, a manifold and other means of controlling the flow of fluid inside the sheath. The distal portion of the inflow/outflow sheath is provided with a plurality of holes. Each hole communicates with one or more of the lumens inside the tube, thereby allowing fluid to flow between the surgical field and sources or sinks located outside the patient. The inflow/outflow sheath thereby allows the surgeon to maintain a clear surgical field and protect the patient from accidental injury while eliminating the need for a third irrigation instrument.
Many surgeons use the endoscope not only for visualizing the surgical site, but also for manipulating the area in surgery. Excessive force on the sheathed endoscope may crush or shear off the plastic ribs on the inner side of the sheath, thus destroying the fluid channels. Excessive force can also break the scope, requiring very expensive repairs or replacement of the scope.